Study casts doubt on some findings about sodium

Are Americans getting mixed messages about how much sodium they should be consuming? Lately, yes, and some of those messages are muddled because studies themselves are muddled, a panel of doctors has concluded.

The Institute of Medicine panel reconfirmed evidence that high sodium in diets is associated with increased risk of stroke and cardiovascular disease. But other evidence in recent medical studies, such as a link between high sodium intake and gastric cancer, for example, was found to be inconclusive.

The analysis also casts doubt on a key direction of the salt wars: that substantial portions of the population should lower sodium intake even more than the recommended upper limit: 2,300 milligrams per day. The average adult in the U.S. consumes 3,400 milligrams a day.

Doctors and nutritionists have hammered home a message that more than 2,300 milligrams of sodium a day has been linked to high blood pressure and, indirectly, to cardiovascular disease. That conclusion appears to stand.

But the analysis casts doubt on ratcheting down intakes toward the minimum recommended level of 1,500 milligrams per day -- either in the general population or for certain sub-groups. They include those over 51, African Americans and anyone with chronic kidney disease, diabetes, hypertension and cardiovascular disease. Together, these groups effectively constitute the majority of the adult population, the panel noted.

In addition, the review found there was some evidence that dipping below the 2,300 threshold could pose risks to people with congestive heart failure whose hearts don’t contract well.

Overall, recent studies were inconsistent in their approaches to measuring sodium intake, the panel found. Among the limits noted were the quality of those measures and the quantity of available evidence. Some under-reported intake, while others over-reported, and still others did not properly collect urine samples used to determine sodium intake. Variations in the way data were collected made it hard for the panel to make comparisons across studies.

The panel recommended adopting standard methodologies for measuring sodium, and said more randomized controlled trials are needed.